Different devices exist that make it possible to maneuver the opening of a blackout curtain for an opening such as a window. One solution consists of motorizing the movement of a head carriage on which one end of the curtain is fastened. This head carriage may comprise guide wheels, in general at least two pairs of wheels, that roll on rolling tracks formed along a rail fastened near the upper edge of an opening to be blacked out.
It is known from JP-A-2005-095364 to incorporate a friction wheel rotated by an electric motor into a carriage. The contact force between the friction wheel and a rolling surface on which it moves is directly related to the performance of the system. The greater this contact force is, the less the contact wheel risks slipping relative to the rail. It is known from DE-A-24 36 753 to suspend a motor carriage from a rail and generate a contact force between a friction wheel and a rail, taking the direction of movement into account. However, the weight of the first curtain panel is not known and may diverge greatly from one piece of equipment to another. Furthermore, that weight being suspended cantilevered relative to the housing, it creates a tilting torque on the housing. There is therefore a need for a fine adjustment of the contact force between the friction wheel and the rail.
It is also known from DE-A-34 37 457 to arrange a motor carriage inside a rail, which makes it possible to make the contact force between the driving wheels and the rail independent of the load being pulled, i.e., the mass of the curtain. However, a particular geometry of the rail must be provided to house the carriage and the rail may not be curved, with a relatively small curve radius, otherwise the carriage may become jammed in a turn.
It is also known from FR-A-2,962,317 to suspend the housing of a motor-driven carriage for opening/closing a curtain from a rail using two members, one of which can tilt relative to the housing, which adjusts the contact force between the rail and a friction wheel supported by that housing. The forces exerted by the curtain on the suspension member, which pivots relative to the housing, can decrease the effectiveness of the drive system contained in the housing.